there are two ways to improve the maximum blood volume * * *
the first way
is to improve the maximum blood volume by improving the role level.
As the level of a character increases, the heart rate will also increase.
not every upgrade will increase, and every level 3 will increase one heart.
the second
raises the maximum blood volume through the challenge.
players need to enter the Hailar Challenge in the big map (as indicated in the figure below), and the maximum blood volume can be increased after the challenge is successful.